Palmitoylation is an important post-translational modification that plays a critical role in regulating protein localization, activity, and stability, as well as multiprotein complex formation. Our preliminary data suggested that DHHC3, a palmitoylating enzyme, plays a critical role in breast cancer growth, invasion, and/or metastasis, at least partly by palmitoylating certain proteins resident in tetrapanin-enriched microdomains. However, very few proteins have been identified as DHHC3 subtrates. Thus, we proposed to comprehensively identify DHHC3 subtrates in breast cancer by integrating our palmitoyl protein identification and site characterization method with triplex SILAC. We established this multiplexed quantitative palmitoylproteomics method in year 1. Here, we applied this multiplexed quantitative palmitoyl-proteomics method to identify DHHC3 substrates in breast cancer MDA-MB 231 cells. We identified over 680 candidate palmioyl proteins, among 70 candidate palmitoyl proteins, among which 70 are candidate DHHC3 subtrates.